2008-11-24_PERMIT FILE - C1996083 (17)

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. Volume IIIA Exhibit 18 Seismic Monitoring - Summary Statement The seismic monitoring network was developed and installed during the period from summer of 2003 through October 2005. In October 2005 the five monitoring points installed within and adjacent to the permit area for the Bowie No. 2 Mine came online as a complete system. This system consists of standard hardware and software and applies standard methods of earthquake seismology. Remote, solar-powered, seismometer stations continuously record and transmit seismic waves via radio to computers residing on a closed local-area network (LAN). Raw data and/or processed results can then be made available to other networks via controlled access. Start of monitoring was in October 2005. Monitoring frequency is continuous with results transmitted by radio as described in the preceding paragraph. Bowie proposes to maintain the monitoring system and collect and report monitoring data until such time as all underground mining is completed at the mine site. Quarterly data summaries and analyses will be prepared and submitted to the DRMS during this period of time. The monitoring program will be terminated and monitoring sites reclaimed after two, consecutive quarters of monitoring indicate no residual seismisity from underground mine workings near the Bruce Park Dam and Bruce Park landslide. An overview of the seismic monitoring network and program are presented in the enclosed report titled Seismic Monitoring Network at Bowie Resources Longwall Coal Mine prepared by Peter Swanson of NIOSH. BRL has developed a preliminary approach to estimate the level of ground shaking that will result from a mining-related seismic event at Bruce Park Dam and the landslide area. As described in the third and fourth quarter 2007 North Fork Valley Seismic Network (NFVSN) Monitoring reports, to provide the basis for determining potential ground motions, the recorded peak horizontal acceleration (PGA) values are plotted as a function of epicentral distance for events during the third and fourth quarters of 2007 and selected larger events in previous quarters (Figure 1). Epicentral distance was used for plotting the ground motions because the mining- related events are very shallow and so epicentral and hypocentral distances are similar. (Epicentral distance is the distance to the epicenter, which is the location of the seismic event on the earth's surface. Hypocentral distance is the distance to the event's hypocenter or the location where the event was initiated at depth.) The majority of PGAs were measured at epicentral distances of less than 10 km from the recording stations (Figure 1). The measurements are shown color-coded in four magnitude bins: Richter magnitude (ML) 1.5 to 1.9, 2.0 to 2.4, 2.5 to 2.9, and 3.0 to 3.4. Only a few events occurred that were large enough to be in the last category. The largest recorded PGA to date is 0.10 g (Figure 1). Figure 1 shows the attenuation relationship of McGarr and Fletcher (2005) for ML 1.75, 2.25, 2.75 and 3.25 plotted against the NFVSN data. This attenuation relationship was developed from coal mining-induced seismicity in the Trail Mountain PR-10 - 1 - 05/08 {? PfRov?D 1//zy/off